During the drilling of oil or gas wells, mud-laden fluid or "drilling mud" is often circulated through the hole for cooling and lubricating the drill bit, and for removing cuttings from the well. Drilling mud comprises a mixture of soil and water, and is usually held in a surface pond or pit adjacent to the well. The drilling mud is pumped into the hole and is then returned to the pit where the various cuttings are deposited.
The drilling mud provides a means of communicating with the bottom of the hole and with the geological formations penetrated by the bit during drilling. By appropriate measurements at the surface, before the drilling mud is returned to the pit, useful data such as the concentration of oil, gas, water, or sulfur in the drilling mud or cuttings, rate of drilling penetration, etc. can be determined through mud analysis. These data are then correlated with depth to provide a readout of information during drilling of the well.
Examination of drilling mud and the cuttings carried thereby is known as mud logging. Although discrete samples of drilling mud can be collected and analyzed, it is preferable to conduct sampling on a continuous basis. For example, the control and amount of information afforded by continuous mud logging is particularly desirable during drilling of exploratory holes, or when the stratigraphy is complicated. The mud sampling chambers of the prior art, however, have had a tendency to fill up and become clogged, which in turn has resulted in analysis of stagnant samples, improper sampling times, and other difficulties adversely affecting the accuracy and reliability of the procedure. Thus, a need has arisen for an improved flow chamber for sampling drilling mud on a continuous basis.